CA2488081A1

CA2488081A1 - Rubber mixtures

Info

Publication number: CA2488081A1
Application number: CA002488081A
Authority: CA
Inventors: Oliver Klockmann; Andre Hasse; Hans-Detlef Luginsland
Original assignee: Degussa GmbH
Current assignee: Evonik Operations GmbH
Priority date: 2003-11-21
Filing date: 2004-11-19
Publication date: 2005-05-21
Also published as: US20050124740A1; PL1533336T3; DE502004008858D1; CN100575402C; EP1533336A1; TW200523310A; EP1533336B1; ATE420920T1; ZA200409287B; DE10354616A1; BRPI0405137A; SI1533336T1; KR20050049376A; ES2320655T3; RU2004133917A; US8236882B2; JP4755411B2; JP2005154769A; CN1629221A; KR101138535B1

Abstract

The invention provides rubber mixtures containing (A) a rubber or mixture of rubbers, (B) a filler, (C) an organosilane of the general formula I
(see formula I) (D) a thiuram accelerator and (E) a nitrogen-containing co-activator, the weight ratio of thiuram accelerator (D) to nitrogen-containing co-activator (E) being equal to or greater than 1.
The rubber mixtures are prepared by mixing the rubber or mixture of rubbers (A), a filler (B), an organosilane of the general formula I (C), a thiuram accelerator (D) and a nitrogen-containing co-activator (E) in a mixing unit.
The rubber mixtures can be used in pneumatic tyres, tyre treads, cable sheaths, hoses, drive belts, conveyor belts, roller coverings, tyres, shoe soles, gaskets and damping elements.

Description

Rubber na3.xtures The invention relates to rubber mixtures, to a process for their preparation and to their use.
It is known to use silanes as adhesion promoters. For example, aminoalkyltrialkoxysilanes, methacryloxyalkyl-trialkoxysilanes, polysulfanealkyltrialkoxysilanes and mercaptoalkyltrialkoxysilanes are used as adhesion promoters between inorganic materials and organic polymers, as crosslinkers and surface-modifying agents (E. P.
Plueddemann, "Silane Coupling Agents", 2nd Ed. Plenum Press 1982).
These adhesion promoters, or coupling or bonding agents, form bonds both to the filler and to the elastomer and accordingly effect good interaction between the filler surface and the elastomer.
It is also known that the use of commercially available silane adhesion promoters (DE 22 55 577) having three alkoxy substituents on the silicon atom leads to the release of considerable quantities of alcohol during and after binding to the filler. Because trimethoxy- and triethoxy-substituted silanes are generally used, the corresponding alcohols, methanol and ethanol, are released in considerable quantities.
It is also known, from DE 10015309, that the use of a mercaptosilane in combination with a long-chain alkylsilane in rubber mixtures leads to increased reinforcement and a reduced hysteresis loss. The alkylsilane is necessary to ensure that the rubber mixture can be processed reliably.
It is further known that methoxy- and ethoxy-substituted silanes are more reactive than the corresponding long-chain alkoxy-substituted silanes and accordingly are able to bind more rapidly to the filler, so that the use of methoxy and ethoxy substituents cannot be dispensed with from a technical and economic point of view.
From DE 10137809 there are known organosilicon compounds of the general formula RO
R'O-Si-R" X,n R'O
n or of the general formula RO
RO S i-R " X m R'O
n wherein R is a methyl or ethyl group, the substituents R' are identical or different and are a Cg-C30 branched or unbranched monovalent alkyl or alkenyl group, aryl group, aralkyl group, branched or unbranched Ca-C3o alkyl ether group, branched or unbranched C2-C3o alkyl polyether group, R" is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent Ci-C3o hydrocarbon group, X is NH~3_n~ where n=1,2,3 and m=1, O(C=0)-R " ' where n=1 and m=1, SH where n=1 and m=1, S where n=2 and m=1-10 and mixtures thereof, S(C=0)-R " ' where n=1 and m=1 or H where n=1 and m=1, where R " ' is a C1-C3o branched or unbranched alkyl or alkenyl group, aralkyl group or aryl group.
Also known, from DE 10223658, are organosilicon compounds of the general formula RO
R O-Si-R - SH
RO
or RO
\ ..
RO-S i-R - SH
./
RO
wherein R is a methyl or ethyl group, the substituents R' are identical or different and are a Cg-C3p branched or unbranched monovalent alkyl group, R" is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-Cso hydrocarbon group, R' is a mixture and the proportion of one component of the mixture is from 10 to 50 mol.~.
Disadvantages of the known rubber mixtures containing mercaptosilanes having long-chain alkoxy groups are the short incubation time and the short Mooney scorch time, which do not ensure reliable processability.
From WO 03/020813 it is known that the Mooney scorch time of silica-containing rubber mixtures can be prolonged by dispensing with the addition, customary in the case of silica-containing rubber mixtures, of diphenylguanidine while at the same time increasing the amount of added thiuram disulfide and at the same time adding a polyalkylene oxide. The addition of a polyalkylene oxide is disadvantageous, because it interferes with the crosslinking density (Technical Report TR 818 of Degussa AG).
The object of the present invention is to provide rubber mixtures, containing mercaptosilanes, which have an incubation time similar to that of polysulfidic organosilanes and accordingly ensure reliable processability.

The invention provides rubber mixtures containing (A) a rubber or mixture of rubbers, (B) a filler, (C) an organosilane of the general formula I

R1 ~S i-R2 R3 q I, wherein the substituents R1 are identical or different and consist of a C1-C12-alkyl group or a R40 group, where R4 is identical or different and is a C1-C3o branched or unbranched monovalent alkyl, preferably methyl, ethyl, propyl or C9-C3o-alkyl group, alkenyl, aryl, aralkyl group or (R5) 3Si group, where R5 is a C1-C3o branched or unbranched alkyl or alkenyl group, R2 is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent Ci-C3o hydrocarbon group, R3 is H, CN or (C=0} -R6 for q=1, where R6 is a Cl-C3o, preferably C5-C2o, particularly preferably C~, branched or unbranched monovalent alkyl, alkenyl, aryl or aralkyl group, (C=O) for q=2 and P=S for q=3, and q=1-3, (D) a thiuram accelerator and (E) a nitrogen-containing co-activator, characterised in that the weight ratio of thiuram accelerator (D) to nitrogen-containing co-activator (E) is equal to or greater than 1, preferably from 1.0 to 4Ø
Natural rubber and/or synthetic rubbers can be used as the rubber (A). Preferred synthetic rubbers are described, for example, in W. Hofmann, Kautschuktechnologie, Genter Verlag, Stuttgart 1980. They may include, inter alia, - polybutadiene (BR) - polyisoprene (IR) - styrene/butadiene copolymers having styrene contents of from 1 to 60 wt.~, preferably from 5 to 50 wt.~ (SBR) 5 - isobutylene/isoprene copolymers (IIR) - butadiene/acrylonitrile copolymers having acrylonitrile contents of from 5 to 60 wt.~, preferably from 10 to 50 wt.~ (NBR) - ethylene/propylene/diene copolymers (EPDM) as well as mixtures of these rubbers.
Solution-SBR, preferably solution-SBR having a vinyl content of at least 50~, may be used as the rubber (A).
In a preferred embodiment, the rubbers may be vulcanisable by means of sulfur.
As the filler (B) there may be used silicate-like fillers, for example precipitated or pyrogenic silicas, o~ carbon black. The silica can have a BET surface area of from 100 m2/g to 250 m2/g.
The organosilane of the general formula I (C) may be a mixture of different organosilanes of formula I.
The mixture of different organosilanes of formula I may contain organosilanes of the general formula I having di f f erent groups R4 .
The organosilane of the general formula I (C) may be a mercaptopropyltrialkoxysilane of the general formula II

R~-S i-( CH2 ) 3-SH
Rl/
II
in which R1 is a mixture of ethoxy, dodecoxy, tetradecoxy, hexadecoxy and octadecoxy in amounts of in each case from 0~ to 100.

The organosilane of the general formula I (C) may be a m~rcaptopropyltrialkoxysilane in which the alkoxy groups R40 are a mixture of ethoxy, dodecoxy and tetradecoxy groups, preferably containing on average from 0.8 to 1.2 ethoxy groups, from 1.2 to 1.6 dodecoxy groups and from 0.4 to 0.8 tetradecoxy groups.
The organosilane of the general formula I (C) may be a mercaptopropyltrialkoxysilane in which the alkoxy groups R40 are a mixture of ethoxy and tetradecoxy groups, preferably containing on average from 0.8 to 1.2 ethoxy groups and from 1.8 to 2.2 tetradecoxy groups.
The organosilane of the general formula I (C) may be a mercaptopropyltrialkoxysilane in which the alkoxy groups R40 are a mixture of ethoxy, hexadecoxy and octadecoxy groups, preferably containing on average from 0.8 to 1.2 ethoxy groups, from 0.8 to 1.2 hexadecoxy groups and from 0.8 to 1.2 octadecoxy groups.
The organosilane of formula I (C) may be oligomerised or polymerised.
The organosilane of formula I (C) may be applied to a carrier. As the carrier there may be used, for example, carbon black, aluminium oxide, wax, thermoplastics, silica or silicates. The organosilane of formula I (C) may have been applied to an inorganic carrier or pre-reacted with an organic or inorganic carrier.
As the thiuram accelerator (D) there may be used thiuram sulfide accelerators, preferably thiuram monosulfides, thiuram disulfides, thiuram tetrasulfides or thiuram hexasulfides, particularly preferably tetrabenzylthiuram disulfide or tetramethylthiuram disulfide.
As the nitrogen-containing co-activator (E) there may be used amine co-activators. Guanidines, preferably diphenyl-guanidine, may be used as the amine co-activator.

o3oa~5 so The rubber mixtures may contain from 10 to 150 parts by weight of filler (B), based on 100 parts by weight of rubber. The rubber mixtures may contain from 0.1 to 20 parts by weight of organosilane of formula I (C), based on 100 parts by weight of rubber. The rubber mixtures may contain from 0.02 to 4 parts by weight, preferably from 0.02 to 1 part by weight, of thiuram accelerator (D), based on 100 parts by weight of rubber. The rubber mixtures may contain from 0 to 2 parts by weight, preferably from 0.1 to 2 parts by weight, particularly preferably from 0.2 to 0.5 part by weight, of nitrogen-containing co-activator (E), based on 100 parts by weight of rubber.
The rubber mixtures may contain from 10 to 150 parts by weight of filler (B), from 0.1 to 20 parts by weight of organosilane of formula I (C), from 0.02 to 4 parts by weight, preferably from 0.02 to 1 part by weight, of thiuram accelerator (D) and from 0 to 2 parts by weight;
preferably from 0.1 to 2 parts by weight, particularly preferably from 0.2 to 0.5 part by weight, of nitrogen-containing co-activator (E); the parts by weight being based on 100 parts by weight of rubber.
The rubber mixtures may contain at least 0.25 part by weight of tetrabenzylthiuram disulfide or tetramethylthiuram disulfide, based on 100 parts by weight of rubber, and not more than 0.25 part by weight of diphenylguanidine, based on 100 parts by weight of rubber.
The rubber mixtures may contain no alkylene oxide.
The rubber mixtures may additionally contain silicone oil and/or alkylsilane.
The rubber mixtures according to the invention may contain further known rubber auxiliary substances, such as, for example, crosslinkers, vulcanisation accelerators, reaction accelerators, reaction retardants, anti-ageing agents, osoa45 so stabilisers, processing aids, plasticisers, waxes, metal oxides and activators.
The rubber auxiliary substances may be used in conventional amounts, which are governed inter alia by the intended use.
Conventional amounts may be, for example, amounts of from 0.1 to 50 wt.~, based on rubber.
As crosslinkers there may be used sulfur or organic sulfur donors.
The rubber mixtures according to the invention may contain further vulcanisation accelerators. Examples of suitable vulcanisation accelerators may be mercaptobenzthiazoles, sulfenamides, guanidines, dithiocarbamates, thioureas and thiocarbonates.
Preferably, sulfenamide accelerators, for example cyclohexylbenzothiazolesulfenamide and/or dicyclohexyl-benzothiazolesulfenamide and/or butylbenzothiazole-sulfenamide, may be used.
The vulcanisation accelerators and sulfur may be used in amounts of from 0.1 to 10 wt.~, preferably from 0.1 to 5 wt.~, based on the rubber used.
The invention also provides a process for the preparation of the rubber mixtures according to the invention, which process is characterised in that the rubber or mixture of rubbers (A), a filler (B), an organosilane of the general formula I (C), a thiuram accelerator (D) and a nitrogen-containing co-activator (E) are mixed in a mixing unit, the weight ratio of thiuram accelerator (D) to nitrogen-containing co-activator (E) being equal to or greater than 1.
Mixing can be carried out at a temperature below 165°C.
Mixing of the rubbers with the filler, optional rubber auxiliary substances and the organosilanes can be carried out in conventional mixing units, such as roll mills, internal mixers and mixing extruders. Such rubber mixtures can usually be prepared in internal mixers, the rubbers, the filler, the organosilanes and the rubber auxiliary substances first being mixed in at from 100 to 170°C in one or more successive thermomechanical mixing steps. The sequence of addition and the time of addition of the individual components can have a decisive influence on the properties of the resulting mixture. Usually, the crosslinking chemicals can be added to the resulting rubber mixture in an internal mixer or on a roll at from 40 to 110°C, and processing to the so-called crude mixture for the subsequent process steps, such as, for example, shaping and vulcanisation, can be carried out.
Vulcanisation of the rubber mixtures according to the invention can be carried out at temperatures of from 80 to 200°C, preferably from 130 to 180°C, optionally under pressure of from 10 to 200 bar.
The rubber mixtures according to the invention can be used in the production of moulded bodies, for example for the production of pneumatic tyres, tyre treads, cable sheaths, hoses, drive belts, conveyor belts, roller coverings, tyres, shoe soles, sealing elements, such as, for example, gaskets, and damping elements.
The invention also provides moulded bodies obtainable from the rubber mixture according to the invention by vulcanisation.
The rubber mixtures according to the invention have the advantage that they possess an incubation time similar to that of rubber mixtures containing polysulfidic organosilanes and accordingly ensure reliable processability.

A further advantage is that the crosslinking density of the rubber mixtures according to the invention does not change in comparison with rubber mixtures having a weight ratio of thiuram accelerator (D) to nitrogen-containing co-activator 5 (E) of less than 1. The advantageous vulcanate data of the mercaptosilane-containing rubber mixtures are retained.

o3oa45 so Examples:
Examples 1-2 The formulation used for the rubber mixtures is shown in Table 1 below. In the table, the unit phr denotes parts by weight based on 100 parts of the crude rubber used.
The silane A used for the example has the structure according to the following formula II

R1 'S i-( CH2 ) 3-SH
1~
R II
where R1 a mixture of ethoxy and R40 groups in a ratio of 1:2, the R40 groups being a mixture of dodecoxy and tetradecoxy in a weight ratio of 70:30.
The silane A is prepared as follows:
In a 10-litre four-necked flask, a mixture consisting of 2.925 kg of mercaptopropyltriethoxysilane (formula II where R1 - CH3CH20) and 4.753 kg of a mixture of 70 wt.~ dodecanol (CH3- (CH2) 11-~H) and 30 wt. ~ tetradecanol (CH3- (CH2) 13-~H) is heated with 1.464 ml of tetra-n-butyl orthotitanate to 110°C, and ethanol that forms is distilled off in vacuo in the course of 4 hours at a maximum of 50 mbar. 6.47 kg (98~
of the theoretical yield) of a colourless, liquid mercapto-propyltrialkoxysilane of formula II are obtained, in which the R1 groups are a mixture of ethoxy, dodecoxy and tetradecoxy groups with on average 1 ethoxy group, 1.5 dodecoxy groups and 0.5 tetradecoxy groups.
In reference mixture 3 and the Examples, the basic mixtures (lst + 2nd step) are identical. They differ only in the amounts of the accelerator DPG and of the ultra-accelerator TBzTD (3rd step) that are used. Reference mixture 1 contains the organosilane Si 69. Because Si 69 is a sulfur donor and the mercaptosilane is not a sulfur donor, this is compensated for by using less sulfur in reference mixture 1 and in reference mixture 2 than in reference mixture 3 and the Example mixtures 1-2 containing the mercaptosilane.
Table 1 Substance Amount Amount Amount Amount Amount [phr] [phr] [phr] [phr] [phr]

1st step Ref. Ref. 2 Ref. 3 Ex. 1 Ex. 2 Buna VSL 5025-1 96 96 96 96 96 Buna CB 24 30 30 30 30 30 ltrasil 7000 GR 80 80 80 80 80 Zn0 3 3 3 3 3 Stearic acid 2 2 2 2 2 aftolen ZD 10 10 10 10 10 ulkanox 4020 1.5 1.5 1.5 1.5 1.5 Protector G35P 1 1 1 1 1 Si 69 6.4 6.4 - -Silane A - - 5.4 5.4~ 5.4 2nd step Batch step 1 3rd step Batch step 2 ulkacit D 2 0.25 2 0.25 0.25 Perkacit TBzTD 0.2 0.6 0.2 0.5 0.75 ulkacit CZ 1.5 1.5 1.5 1.5 1.5 Sulfur 1.5 1.5 2.2 2.2 2.2 The polymer VSL 5025-1 is a solution-polymerised SBR
copolymer from Bayer AG having a styrene content of 25 wt.~
and a butadiene content of 75 wt.~. The copolymer contains 37.5 phr of oil and has a Mooney viscosity (ML 1+4/100°C) of 50.
The polymer Buna CB 24 is a cis-1,4-polybutadiene (neodymium type) from Bayer AG having a cis-1,4 content of at least 96~ and a Mooney viscosity of 44 ~ 5.

o3oa45 so Ultrasil 7000 GR is a readily dispersible silica from Degussa AG and has a BET surface area of 170 m2/g.
The coupling reagent Si 69, a bis-(triethoxysilylpropyl) tetrasulfide, is a product from Degussa AG.
The aromatic oil used is Naftolen ZD from Chemetall, Vulkanox 4020 is 6PPD from Bayer AG and Protektor G35P is an anti-ozone wax from HB-Fuller GmbH. Vulkacit D (DPG, diphenylguanidine) and Vulkacit CZ (CBS) are commercial products from Bayer AG. Perkacit TBzTD (tetrabenzylthiuram disulfide) is a product from Flexsys N.V..
The rubber mixture is prepared in three steps in an internal mixer, according to Table 2.

Table a:
Step 1 settiags Mixing unit Werner & Pfleiderer GK 1.5E

Friction 1:1 Speed 60 miri 1 Ram pressure 5.5 bar Volume when 1.6 1 empty Degree of 0.56 filling Flow temp. 70C

ixiag operation 0 to 1 min Buna VSL 5025-1 + Buna CB 24 1 to 2 min '/z Ultrasil 7000 GR, ZnO, stearic acid, Naftolen ZD, silane 2 to 4 min ~4 Ultrasil 7000 GR, Vulkanox 4020, Protector G35P

4 min clean 4 to 5 min mix with variation in speed in order to maintain the temperature of 140-150C

min clean 5 to 6 min mix and complete the operation Batch temp. 140-150C

Storage 24 h at room temperature 030a45 SO
step a Settings fixing unit as in step 1 with the exception of:

Speed 70 miri 1 Degree of 0.54 filling Flow temp. 70C

fixing operation 0 to 2 min break up step 1 batch 2 to 5 min maintain batch temperature of 145-150C

by varying speed 5 min complete the operation Batch temp. 145-150C

Storage 4 h at room temperature Step Settiags fixing unit as in step 1 with the exception of Speed 4 0 min-1 Degree of 0.52 filling Flow temp. 50C

Mixing operation 0 to 2 min step 2 batch + Vulkacit C2 + Vulkazit D +

Perkacit TBzTD + sulfur 2 min complete the operation and form rolled sheet on laboratory roll mill (diameter 200 mm, length 450 mm, flow temperature 50C) homogenisation:

cut in 3* on the left, 3* on the right and fold over and turn over 8* with a narrow roll gap ( 1 mm ) and 3* with a wide roll gap (3.5 mm) and then draw out a rolled sheet Batch temp. 90-100C

The general process for the preparation of rubber mixtures and their vulcanates is described in "Rubber Technology Handbook", W. Hofmann, Hanser Verlag 1994.
Testing of the rubber is carried out according to the test methods indicated in Table 3.

osoa45 so Table 3 Physical testing Standard/
Conditions 1+4, 100C (3rd step) DIN 53523/3, ISO 667 Start-of-vulcanisation behaviour, DIN 53523/4, ISO 667 ulcameter test, 165C DIN 53529/3, ISO 6502 Dmax - Dmin t10~

t80~ - t20~

Ring tensile test, 23C DIN 53504, ISO 37 Tensile strength Tensile stress Ultimate elongation Shore A hardness, 23C DIN 53 505 Ball rebound, 60C DIN EN ISO 8307 steel ball mm, g DIN abrasion, 10 N force DIN 53 516 iscoelastic properties DIN 53 513, ISO 2856 0 and 60C, 16 Hz, 50 N i preliminary force and 25 N

amplitude force Complex modulus E* (MPa) Loss factor tan b (-) Goodrich flexometer test DIN 53533, ASTM D 623 A

0.250 inch stroke, 25 min, 23C

Contact temperature (C) Puncture temperature (C) Permanent set ($) Table 4 shows the rubber-technological data for the crude mixture and the vulcanate.

Table 4 Crude mixture data Feature: Unit: Ref.1 Ref.2 Ref.3 Ex.1 Ex.2 ML 1+4 at 100C, 3rd ME 62 63 55 59 58 ste Scorch time, t5 min 27.1 33.7 9.4 19.2 17.5 Scorch time, t35 min 36.4 40.9 12.4 24.1 21.1 Vulcanate data Feature: Unit:

Tensile stren th MPa 13.1 13.7 13.2 14.7 12.2 Tensile stress 100% MPa 1.7 2.0 1.7 1.8 1.8 Tensile stress 300% MPa 9.1 11.5 11.5 11.5 11.8 Tensile stress 300%/100% 5.4 5.8 6.8 6.4 6.6 Ultimate elon ation % 370 335 325 340 300 Shore A hardness SH 60 64 56 57 60 Ball rebound, 60C % 65.8 68.1 75.8 75.2 75.6 DIN abrasion mm3 85 73 68 59 61 Contact tem erature C 56 56 53 53 51 Puncture tem erature C 101 98 94 93 91 Permanent set % 3.4 2.0 3.5 2.2 2.2 Dyn. modulus of elasticity[MPaj 16.0 16.9 9.3 10 10 E* 0C

Dyn. modulus of elasticity[MPa] 7.3 8.2 5.8 6.2 6.3 E* 60C

Loss factor tan 8, [-] 0.369 0.359 0.306 0.310 0.312 Loss factor tan 8, [-] 0.099 0.088 0.069 0.070 0.062 Reference mixture 2 shows the effect of the changed thiuram/amine co-activator ratio on a rubber mixture which, like reference mixture 1, contains Si 69. If reference mixture 1 is compared with reference mixture 2 it will be seen that the scorch time is within the same order of magnitude.
If reference mixture 1 is compared with reference mixture 3, it is clear that reference mixture 3, which contains silane A, exhibits marked disadvantages in terms of processing behaviour. It has lower scorch times, which has an adverse effect on the processability of the accelerated finished mixture (e. g, on extrusion). The processing osoa45 so reliability is impaired as a result, because pre-crosslinking is possible.
At the same time, reference mixture 3 containing the above-mentioned silane has considerable advantages in terms of the vulcanate data. The tensile stress at 300 elongation and the reinforcement factor are higher. At the same time, the elasticity (ball rebound) is considerably higher and the DIN abrasion is markedly improved. This shows a markedly higher coupling yield between the filler and the polymer, which is caused by silane A. The tan 8 at 60°C, which is correlated with the rolling resistance, is also markedly better for reference mixture 3.
The two Examples 1 and 2 differ from reference mixture 3 in the composition of the accelerator system. The amount of the co-activator DPG has been markedly reduced and that of the ultra-accelerator TBzTD has been considerably increased. The crude mixture data of these mixtures are improved thereby. The scorch time is almost doubled compared with reference mixture 3. In mixtures containing Si 69 (reference mixture 2 compared with reference mixture 1), this is not the case.
The effect of the changed activator ratio on the vulcanisation behaviour is shown in Figures 1 and 2.
As will be seen in Figure 1, the change in the accelerator ratio in the case of the reference Si 69 has virtually no effect on the incubation time. In Figure 2, on the other hand, the positive effect of the accelerator variation on the incubation time is clear. The beginning of the increase in torque is markedly displaced to longer times.
Significantly higher processing reliability is obtained as a result. In addition, the marching modulus of reference mixture 3 is eliminated in Examples 1 and 2. These results are surprising because, when larger amounts of TBzTD are used, even more rapid vulcanisation would be expected.
Accordingly, an effect is obtained for silane A that cannot be observed with Si 69.
Changing the accelerator combination brings about virtually 5 no change in the vulcanate data. The crude mixture properties of the silane A can be markedly improved without impairing the good vulcanate data.
10 Examples 3-8:
The formulation used for the rubber mixtures described here is given in Table 5 below.
The rubber mixture is prepared in three steps in an 15 internal mixer according to Table 2.
Testing of the rubber is carried out according to the test methods indicated in Table 3.

' CA 02488081 2004-11-19 osoa45 so Tsble 5 Substance Amount Amount Amount Amount Amount Amount Amount Amount IP1'irlIPhrlIPhrlIPhrlIPhrlIP1'irIIPhrlIPt~rl 1st step Ref. Ref. Ex. Ex. Ex. Ex. Ex. Ex.

Buna VSL 5025-196 96 96 96 96 96 96 96 Buna CB 24 30 30 30 30 30 30 30 30 Ultrasil 7000 80 80 80 80 80 80 80 80 GR

Zn0 3 3 3 3 3 3 3 3 Stearic acid 2 2 2 2 2 2 2 2 aftolen ZD 10 10 10 10 10 10 20 10 ulkanox 4020 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Protector G35P1 1 1 1 1 1 1 1 Si 69 6,4 - - - - - - -Silane A - 5.4 5.4 5.4 5.4 5.4 5.4 5.4 2nd step Batch step 3rd step Batch step ulkacit D 2 2 0.25 0.25 0.25 0.25 0 0 Perkacit TBzTD0.2 0.2 0.25 0.5 0.75 1 0.75 1 ulkacit CZ 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Sulfur 1.5 2.2 2.2 2.2 2.2 2.2 2.2 2.2 The rubber-technological data for the tested mixtures from Table 5 are shown in Table 6.

Table 6 Crude mixture data Feature: Unit: Ref.Ref. Ex.3Ex.4 Ex.5Ex.6 Ex.7Ex.

ML 1+4 at 100C, 3rd ME 63 55 57 57 58 63 56 58 ste Scorch time t5 min 24.49.4 21.218.7 21.322.2 23.328.5 Scorch time, t35 min 30.912.4 26.523.0 25.025.7 29.035.6 Dmax-Dmin dNm 16.616.4 17.715.8 17.624.8 14.817.4 t 10% min 1.6 1.0 2.1 1.9 1.9 1.3 2.3 2.3 t 80% - t 20~o min 2.2 7.1 5.0 2.3 1.5 1.5 2.4 2.7 Vulcanate data Feature: Unit:

Tensile stren th MPa 13.713.2 12.811.2 12.012.2 10.811.3 Tensile stress 100% MPa 1.7 1.7 1.5 1.7 1.9 1.9 1.8 2.0 Tensile stress 300% MPa 9.4 11.5 9.1 11.1 12.011.4 11.3---Ultimate elon ation % 380 325 365 300 300 315 315 275 Shore A hardness SH 62 56 56 57 59 62 58 60 Ball rebound 60C % 66.075.8 70.071.0 72.071.1 71.872.5 DIN abrasion mm3 72 68 57 49 50 57 49 52 Contact tem rature C 58 53 56 52 51 55 49 49 Puncture tem eratureC 101 94 104 93 91 95 86 84 Permanent set % 2.9 3.5 3.1 1.8 1.8 3.2 1.6 1.6 Dyn. modulus of elasticity[MPaj 16.19.3 11.010.2 10.912.3 9.7 10.2 E*, 0C

Dyn. modulus of elasticity[MPaj 7.6 5.8 6.6 6.6 6.9 7.7 6.6 6.8 E*, 60C

Loss factor tan 8 [-] 0.4180.3060.3930.3820.3870.3870.3590.370 Loss factor tan 8 [-j 0.0980.0690.0890.0750.0700.0690.0640.062 As will be seen from the results of Table 6, the change in the ratio of DPG to TBzTD brings about a marked improvement in the processing behaviour of the crude mixtures compared with reference mixture 5. Mooney scorch, t 10~ time and accordingly the incubation time are raised significantly and in some cases reach the level of reference mixture 4.
At the same time, a profile of rubber values which is comparable to that of reference mixture 5 and is markedly superior to that of reference mixture 4 is obtained.

Examples 9-10:
The formulation used for the rubber mixtures described here is shown in Table 7 below.
MPTES in this example is y-mercaptopropyltriethoxysilane, which is obtainable as VP Si263 from Degussa AG, and silane B, which can be prepared according to Example 9 of EP 0958298 B1, is 3-octanoylthio-1-propyltriethoxysilane.
The rubber mixture is prepared in three steps in an internal mixer, according to Table 2.
Testing of the crude mixtures is carried out according to the test methods indicated in Table 3.
Table 7 Substance Amount AmountAmount Amount [phr] [phr] [phr] [phr]

1st step Ref. Ex. Ref. Ex. 10 Buna VSL 5025-196 96 96 96 una CB 24 30 30 30 30 Ultrasil 7000 80 80 80 80 GR

Zn0 3 3 3 3 Stearic acid 2 2 2 2 aftolen ZD 10 10 10 10 ulkanox 4020 1.5 1.5 1.5 1.5 Protector G35P1 1 1 1 ES 2.4 2.4 - -Silane B - - 8.9 8.9 2nd step Batch step 3rd step Batch step ulkacit D 2.0 0.25 2.0 0.25 Perkacit TBzTD0.2 0.60 0.2 0.60 ulkacit CZ 1.5 1.5 1.5 1.5 Sulfur 2.2 2.2 2.2 2.2 Table 8 shows the results of the crude mixture tests for the tested mixtures from Table 7.

Table 8 Crude mixture data Feature: Unit: Ref.6 Ex.9 Ref.7 Ex.lO

ML 1+4 at 100C, 3rd ME 63 74 55 62 ste Scorch time t5 min 8.4 23.3 18.9 48.9 Scorch time t35 min 11.0 28.1 26.5 58.1 Dmax-Dmin dNm 13.5 22.4 15.4 18.7 t 10% min 0.8 1.0 1.8 3.7 t 80% - t 20% min 2.1 2.4 5.3 _ 11.1 As already shown in the preceding Examples, in the case of these two mercapto-functional silanes too, a change in the accelerator ratio leads to advantages in processing reliability. Both the scorch times and the t 10~ time are improved in Examples 9 and 10 as compared with their two reference mixtures 6 and ?.

Claims

1. Rubber mixtures, containing (A) a rubber or mixture of rubbers, (B) a filler, (C) an organosilane of the general formula I
wherein the substituents R1 are identical or different and consist of a C1-C12-alkyl group or a R4O group, where R4 is identical or different and is a C1-C30 branched or unbranched monovalent alkyl, alkenyl, aryl, aralkyl group or (R5)3Si group, where R5 is a C1-C30 branched or unbranched alkyl or alkenyl group, R2 is a branched or unbranched, saturated or unsaturated, aliphatic, aromatic or mixed aliphatic/aromatic divalent C1-C30 hydrocarbon group, R3 is H, CN or (C=O) -R6 for q=1, where R6 is a C1-C30 branched or unbranched monovalent alkyl, alkenyl, aryl or aralkyl group, (C=O) for q=2 and P=S for q=3, and q=1-3, (D) a thiuram accelerator and (E) a nitrogen-containing co-activator, characterised in that the weight ratio of thiuram accelerator (D) to nitrogen-containing co-activator (E) is equal to or greater than 1.

2. Rubber mixtures according to claim 1, characterised in that they contain sulfenamides.

3. Rubber mixtures according to claim 1, characterised in that the thiuram accelerator (D) is a thiuram monosulfide, a thiuram disulfide, a thiuram tetrasulfide or a thiuram hexasulfide.

4. Rubber mixtures according to claim 1, characterised in that the nitrogen-containing co-activator (E) is an amine co-activator.

5. Rubber mixtures according to claim 1, characterised in that the organosilane (C) is applied to an inert organic or inorganic carrier or pre-reacted with an organic or inorganic carrier.

6. Rubber mixtures according to claim 1, characterised in that the organosilane (C) is oligomerised or polymerised.

7. Rubber mixtures according to claim 1, characterised in that the organosilane (C) is a mercaptopropyltrialkoxy-silane of formula II
in which R1 is a mixture of ethoxy, dodecoxy, tetradecoxy, hexadecoxy and octadecoxy in amounts of in each case from 0% to 100%.

8. Rubber mixtures according to claim 1, characterised in that the rubber (A) is a solution-SBR.

9. Process for the preparation of rubber mixtures according to claim 1, characterised in that the rubber or mixture of rubbers (A), a filler (B), an organosilane of the general formula I (C), a thiuram accelerator (D) and a nitrogen-containing co-activator (E) are mixed in a mixing unit.

10. Use of the rubber mixtures according to claim 1 in pneumatic tyres, tyre treads, cable sheaths, hoses, drive belts, conveyor belts, roller coverings, tyres, shoe soles, gaskets and damping elements.